Interactions of mixed organic contaminants in uptake by rice seedlings

Abstract

a b s t r a c tUptakes of o-chlorophenol (CP), 2,4-dichlorophenol (DCP), trichloroethylene (TCE), and atrazine (ATR), as single and mixed contaminants, by roots and shoots of rice seedlings (Oryza sativa L.) from hydroponic solutions were measured following a 48-h exposure of plant roots. As single contaminants, the concentrations of CP, DCP, and ATR in rice roots and shoots increased significantly with increasing concentrations in external solutions; however, TCE concentrations in rice roots and shoots decreased with increasing external TCE concentration or the exposure time. The observed bioconcentration factors (BCFs) of CP and DCP with roots and the BCF of ATR with shoots approximated the equilibrium values according to the partition-limited model. The BCF of DCP with shoots was about 30% of the partition limit, due to insufficient water transport into plants for DCP. In the ATR-CP-DCP mixed system, the BCFs of CP and DCP with both roots and shoots decreased significantly with increasing contaminant concentrations due to the enhanced mixed-contaminant phytotoxicity, as manifested by the greatly reduced plant transpiration rate. In the ATR-CP-DCP mixture system, the BCFs of ATR with roots at low concentrations were comparable with those for ATR alone, whereas the BCFs increased at high concentrations for an unknown reason. In the TCE-DCP system, TCE concentrations in roots increased with increasing TCE in external solutions, while TCE concentration in shoots stayed steady because of the strong TCE exchange at the air-leaf interface. The BCF of DCP with roots was comparable with that of DCP alone because there was no significant effect of added TCE on the plant transpiration rate.

Transport via xylem of trichloroethylene in wheat, corn, and tomato seedlings

“…* P < 0.05. *** P < 0.001. the volume of the final external solution between TCE treatments, indicating that the effect of TCE uptake on plant transpiration rate was negligible, similar to the results in previous report [14].…”

“…3). Similar to a previous report that TCE in plant could be taken up via shoots from air (foliar uptake) and transported to roots [14], TCE was detected in the final external solutions of control treatments (control 2) in experiment 3 that were not contaminated with TCE before experiment. Meanwhile, TCE was also detected in the dewdrops collected from control 2 in experiment 3.…”

“…After a 22-h plant uptake, the TCE concentration in nutrient solution showed 96%, 97%, 95% and 92% reductions, respectively. The ratio of TCE concentration in xylem sap to that in final external solution (TSFC) in wheat seedling in the present study was not constant ( Table 2); it decreased with increasing initial or final TCE concentration in final external solution, as has been found with rice seedlings [14]. These observations disagree with the hypothesis that the TSCF of a contaminant should be independent of its concentration in external solution [4].…”

“…It has been widely detected in groundwater and surface waters as a result of manufacturing, use, and disposal of the chemical [13]. Previously, we studied the uptake of TCE by rice seedlings from nutrient solution with and without coexisting organic compounds [12,14]. Results from single-TCE experiments indicated that TCE concentrations in rice roots and shoots decreased with the TCE concentration in 0304-3894/$ -see front matter © 2010 Elsevier B.V. All rights reserved.…”

“…doi:10.1016/j.jhazmat.2010.06.055 external solutions or the exposure time. There was no steady root concentration factor (RCF) and shoot concentration factor (SCF), significant difference with other compounds, such as atrazine, o-chlorophenol and 2,4-dichlorophenol [14], as well as Lindane [1], O-methylcarbamoyloximes, substituted phenylureas [4], and phenanthrene. Because of the high TCE volatility from plant leaves to air, the potential for reverse TCE vapor uptake by leaves could thus interfere with the net TCE transport into plant roots and the subsequent translocation into shoots.…”